Various kinds of filled pasta, for example, tortellini, ravioli, agnolotti, etc., constituted by one or more pieces of rolled pasta dough enclosing a filling, are known in the food field.
In pasta of these types, the individual pieces of rolled dough are prepared from a main sheet made of conventional dough comprising semolina and eggs, whereas the filling is prepared in accordance with a recipe comprising various ingredients such as meat, ham, cheese, spices, etc., suitably selected and mixed according to the flavour to be conferred on the filled pasta.
It is also known that the preparation of the aforementioned filled pasta requires a series of steps having the purpose of enclosing the filling between one or more pieces of pasta and forming the desired type of pasta.
For example, during the preparation of tortellini, the filling is metered onto a piece of pasta dough which is folded so as to house the filling in a kind of pouch.
The edges of the folded piece are then sealed and the opposite ends of the folded piece are superimposed and pressed together to form the tortellino.
Once the filled pasta has been formed it can undergo a stabilizing step to produce a fresh product, and possibly a subsequent drying step to produce a dried product.
A recognized disadvantage of commercial filled pasta, particularly dried filled pasta, is poor hydration of the filling during cooking in water, which in turn leads to the production of a cooked pasta the consistency and palatability of which do not satisfy the consumer's expectations.
In fact, in cooked filled pasta, the poorly hydrated filling feels substantially hard and "dry" on the consumer's palate and the consumer also notices a different consistency between the filling and the pasta which, on the other hand, is soft after cooking.
To prevent the aforementioned problem, some technical means have been proposed and sometimes adopted in the past for creating one or more passageways for the cooking water into the pasta envelope housing the filling.
U.S. Pat. No. 2,950,978 describes a method of preparing dried ravioli in which holes are formed in the central portion of the pasta envelope formed by two superimposed pieces housing the filling, so as to promote the escape of moisture from inside the ravioli during drying and to improve the rehydration of the filling during cooking.
This method has various disadvantages, amongst which is the need to provide an additional step in the production cycle for forming the holes in the pasta envelope which, amongst other things, is not easy to perform on an industrial scale.
Patent EP 0 439 806 describes a method of preparing filled dried pasta such as ravioli and tortellini, in which at least one passageway is created between the superimposed and sealed edges of the pasta envelope, putting the filling into communication with the environment outside the pasta.
According to one embodiment described in this patent, this is effected by first of all inserting a needle between the superimposed edges of the pasta envelope, then sealing the edges by pinching and, finally, withdrawing the needle, thus producing a passageway between the superimposed edges.
Alternatively, according to a second embodiment described in the above-mentioned patent, the superimposed edges of the pasta envelope are sealed by means of special pinching moulds which have interruptions in one or more sections of their pressure surfaces so that these sections of the superimposed edges of the pasta envelope are not sealed.
However, the first embodiment mentioned above has the disadvantage that it is necessary to provide two additional steps in the production cycle (the insertion and withdrawal of the needle) which render this method uneconomic and difficult to implement.
Moreover, for the additional steps, it requires the availability of fairly complex apparatus which may be complicated and difficult to operate automatically in synchronism with the pinching.
Finally, the filled pasta produced by the above-mentioned method has the disadvantage that the passageways created therein tend to collapse during cooking, in fact blocking the path of the water towards the filling.
The second above-mentioned method described in EP 0 439 806, on the other hand, has the disadvantage that no passageway is in fact created between the superimposed edges of the pasta envelope since, even in the sections of the piece of pasta which are not sealed, these edges are nevertheless in contact so that the filling is not rehydrated during cooking or is rehydrated to a very limited extent.